Efforts to rescue an Australian research team whose cruise ship became trapped in ice off Antarctica on Christmas Day took a step backward Monday when the icebreaker sent to free the ship was forced to retreat to open water. The Australian icebreaker Aurora Austalis was buffeted by 30-mph winds and snow showers as it ground toward the MV Akademic Shokalskiy, a Russian ship with 74 people aboard, the Australian Maritime Safety Authority reported.